Monitor and results computer system

ABSTRACT

System used for aiding the operation of processes occurring in a power generation plant is disclosed which includes a logging technique for transforming input data from various pickup points into a universal, named system variable format usable by all system functions. Specified changes in time or in any system variable can cause a given log to be triggered into a storing state, or an outputting state wherein the stored data is outputted by a printer in a page oriented log print-out format. Also included in the system is a sequence of events interrupt technique wherein the detection devices located within the protective circuits are corrected for their respective time delays between the sensing time of a measured condition and the actuation time of the associated switching contacts. The correction is achieved by storing the predetermined values of the time delays associated with each of the detection devices, and subtracting such stored time delay values from the system detected times of actuation of the respective switching contacts, thereby deriving a corrected sequence of events indicating the correct order of occurrence of the events at the detection devices and, consequently, the initial cause of the event. The system also includes an alarming technique wherein alarm limit values are assigned for a measured system variable at a given point in the system, and realarm values are calculated so that realarming occurs when the measured system variable departs from the last alarmed value by a significant amount of change, thereby employing system discretion in selecting only the most important alarm conditions to be outputted. A CRT device is used for displaying the alarm information and operates with a reduced line format for those alarms acknowledged by the operator. Entry, removal and presentation of alarm data on the CRT screen is designed to present the data in a simple and easily understandable manner while maximizing the amount of data presented.

United States Patent 1 Summers et al.

[ MONITOR AND RESULTS COMPUTER SYSTEM [75] Inventors: William A. Summers, North l-laledon; Betty L. Christy, Radburn, both of N.J.; Joseph V. Sweeney, Manhasset, NY.

[73] Assignee: Ebasco Services Incorporated, New

York, NY.

[22] Filed: June 3, 1974 [21] Appl. No.: 475,987

Related US. Application Data [62] Division of Ser. No. 308,770, Nov. 22, 1972, Pat. No.

235/151.35, 152, 153 AB, 153 EN, 156; 307/204, 211, 219; 318/564; 328/117, 137, 147, 148, 154, 158; 340/1461 BE, 213 G; 444/1 [56] References Cited UNITED STATES PATENTS 5/1972 Pferschet a1. ..30'//219x PrimaryExamineF-R. Stephen Dildine, Jr. Attorney, Agent, or Firm-Kenyon & Kenyon Reilly Carr & Chapin j [57] 1 ABSTRACT System used for aiding the operation of processes occurring in a power generation plant is disclosed which includes a logging technique for transformingtinput 1 Dec. 16, 1975 data from various pickup points into a universal, named system variable format usable by all system functions. Specified changes in time or in any system variable can cause a given log to be triggered into a storing state, or an outputting state wherein the stored data is outputted by a printer in a page oriented log print-out format; Also included in the system is a sequence of events interrupt technique wherein the detection devices located within the protective circuits are corrected for their respective time delays between the sensing time of a measured condition and the actuation time of the associated switching contacts. The correction is achieved by storing the predetermined values of the time delays associated with each of the detection devices, and subtracting such stored time delay values from the system detected times of actuation of the respective switching contacts, thereby deriving a corrected sequence of events indicating the correct order of occurrence of the events at the detection devices and, consequently, the initial cause of the event. The system also includes an alarming technique wherein alarm limit values are assigned for a measured system variable at a given point in the system, and realarm values are. calculated so that realarming occurs when the measured system variable departs from the last alarmed value by a significant amount of change, thereby employing system discretion in selecting only the most important alarm conditions to be outputted. A CRT device is used for displaying the alarm information and operates with a reduced line format for those alarms acknowledged by the operator. Entry, removal and presentation of alarm data on the CRT screen is designed to present the data in a simple and easily understandable manner while maximizing the amount of datapresented.

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55L/EVED KiLuE fiw/vrf/wswce CHECKING MAWMM/YCE Our/ urcS/GNALS ALUE 9 MONITOR AND RESULTS COMPUTER SYSTEM This application is a division of US. Pat. Application Ser. No. 308,770, filed on Nov. 22, 1972, and now US. Pat. Ser. No. 3,855,456, issued on Dec. 17, 1974.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a monitor and results computer system, and more particularly to a system which provides operation, performance and historical data for continuously aiding the operation of a power plant.

2. Description of the Prior Art The conventional manner of handling log information to an operator is to have a scanning device, that is program controlled to convey information into the memory unit of a CPU. The log is a group of data which you identify by designating the log number. The log has a list of points and a value. The logging device can type out the identification of the log, time, point Identification Number(s), and the value(s). The storage of the logging device is the piece of paper. If one is activating the log every 5 minutes, 5 minutes later the log program will be scheduled to gather. the data for the log. From the operators standpoint, the human standpoint, he sees what is going on by looking back at the lines on the piece of paper. To accomplish this may require one typewriter per log which is impractical.

In such state of the art printing devicesused for printing log data, a large number n areplaced in a format wherein generally a single log occupies a line on the printer. A log having a large number, such as 100 variables, would extend across the single line and the resultant printing paper was very wide. On the next line, a different log was printed. As a result of this type of format, a relatively complicated program is required with new headings being retyped for each new time a log is outputted. It is noted that other than the time dependent presentation of a printout, a demand dependent or a demand-on-program type of printout could be employed. For example, in a demand dependent set up, a user requests a log which is then assembled in a computer and then printed out on a typewriter. This typewriter was, according to the state of the art, conventionally a wide-carriage typewriter employing mechanical printing and the printed record on paper was the memory. The mechanical typewriters are used because of their adaptability to printing of a character at a time. On the other hand, printers using non-impact printing techniques are perhaps more ideally suited from the standpoint of the relative freedom from the high maintenance associated with the impact type printers and from the standpoint of speed. However, non-impact printers are not suitable to the applications in the conventional log data storage and printing systems because such systems have a printout format which involves the writing of a character at a time. This character at a time printout format is incompatible with the non-impact printers because the chemical preparation and development processes on such non-impact printers generally requires a relatively short interval of time between the chemical preparation and development steps of printing. Thus, when employing the state of the art non-impact printer in the conventional log data system, if the time interval between the printing of adjacent line is too long, then the chemical bath would overdevelop and wash out those lines which were not removed from development in time.

According to some prior art log printinig formats, a new heading comprising the various names identifications is retyped for each new line. Also, in logging systems used therewith, a demand panel is used to operate in conjunction with a program and special log programs containing lists for each special log. The program consisted of lists in the memory of the members (the names). These lists in the computer memory consisted essentially only of the names while a directory contained the addresses or locations of the names in the memory. A secondary memory device, such as a drum, contains the contents or value of data associated with the names in the memory.

Also, in many supervisory and control systems existent in power plants, overload and protective devices are employed. These devices are connected within a protective circuit and, upon their actuation, provide the system with an indication as to the source of a problem within the power plant, such as a loss of generator power or a boiler trip. Contact changes from the protective circuit network, including the overload devices and protective relays, were incorporated into computer systems and attempts to program the computer to indicate the relays or other protective devices which were activated and the times of activation of their switchingrcontacts have met with common problems.

The protective circuits commonly include a multiplicity of trip devices, such as relays and switches. When a trip condition exists, one or more relays or trip devices are energized and their associated contacts are switched. For each given relay that is activated by a plant condition, there often is one or more auxiliary relays within the protective network that is also activated directly or indirectly as a result of the actuation of the first relay. For example, a first relay switch may have switching contacts which cascade into auxiliary switches which eventually cause a further relay to be activated. Therefore, even though a trip condition is initially sensed at a first relay, signals may be produced in the system which cause an auxiliary relay(s) or trip(s) to occur which may, in turn, indirectly switch other contacts in the system. Because of the hardware associated with the protective system, the contacts of the auxiliary relay(s) may switch over before the final contact that feeds the computer from the initial relay is energized. As a result, the computer or control system incorrectly sees the contacts of the auxiliary relay(s) being switched ahead of the contacts of the initial relay and interprets this as a trip caused by the function of the auxiliary relay. The computer also records the closing or switching of the other devices in the protective circuit and associated or effected plant devices, and records their respective times of occurrence of switch ing and the status of all the devices.

Thus, another problem existing in the prior art monitoring and control systems for power plants is that, because of the different delays associated with the individual relay and tripping devices between the precise time of the occurrence of the alarm condition or event and the actuation of the contacts of such devices, the monitoring and control system indicates the incorrect cause of the event since the system is made aware of such event only upon the actuation of the contacts.

Conventional alarming systems, such as those used in power plants, provide scanning devices which compare desired system characteristics, such as a boiler temperature, to stored low and/or high alarm set points previously designated or calculated for that point. The alarm information status is output on printers, typewriters and on trouble location annunciators providing audible and/or visible warnings of an alarm condition. One problem existing in conventional alarming systems is that a plant emergency may result in a multiplicity of alarms being set off almost simultaneously, such as those due to a failure of the main turbine which in turn interacts with other equipment so as to cause other alarms to be actuated. In some systems, in addition to both high and low alarm limits being set for a particular device, there is provided one or more realarm conditions which are set to occur when a point previously in alarm is detected as having changed a prescribed significant amount, either above or below the last alarmed value. Even here, often this prescribed significant change, hereinafter referred to as delta, is normally small to detect and follow or track the deviations of the value once it is no longer normal. The large transients induced by the loss of the equipment result in the occurrence of several alarms almost continuously being set off for the given equipment and any related plant systems.

Alarm status information is presently being output on printers, typewriters, annunciators and CRT devices. It has been found that the outputting of alarm information by such devices is often confusing or unnoticed to the human understanding because of both the large amount of information being simultaneously displayed as well as the format by which such information is presented.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a monitor and results computer system which is both practical and efficient from the standpoint of computer storage cost, processing time and outputting.

It is another object to provide a logging system which permits the equivalent of wide page printout on narrow paper.

It is another object to provide a logging system which is able to easily change the log members.

It is another object to provide a logging system wherein the stored data is universally usable by all system functions.

It is another object to provide a logging system wherein the log page information in the memory is compacted together in an easily printable form, with minimum processing required.

It is another object to permit storage of such information in a second level memory, instead of on paper.

It is another object to provide a logging system which can easily process via the log name, the defined variables of that log.

It is another object to be able to output both past and present data without the need of continuously outputting.

It is another object to provide a logging system which can make any log available on demand, or upon the occurrence of a condition or event.

It is another object to provide a logging system which generates data on a page at a time output basis, thereby making effective use of non-impact low maintenance printers.

It is another object of the present invention to provide a monitoring and control system which produces the actual and correct sequence of events interrupts occurring in the plant overload and protective devices.

It is another object of the present invention to provide outputting of alarm information in a simple and easily understandable manner.

It is another object to provide current, pertinent alarm information to the human operator which is determined as being the most significant.

It is another object to provide an intelligent reduction in the amount of alarm information presented to the human in a given system.

It is another object to provide a CRT display of alarm information which is easy to understand and is formatted to provide only the necessary alarm information arranged in a logical fashion.

It is another object to provide a CRT display for alarm information which is formatted to maximize the amount of data presented.

It is a further object of the present invention to provide a system which compensates and corrects for failure of any of the input devices measuring the system variables.

These and other objects are achieved by the present invention which provides a logging system within the monitor and results computer system wherein analog to digital input data is presented to the computer system from monitoring devices, such as transducers and thermocouples located at various pickup points external to the computer system. The input data is scanned and transformed into a universal, named system variable format usable by all system functions. The format includes the name identification of the variable, the value of the system variable, the quality of the data and the time at which data is obtained. The name or member of each log is defined by the format. Triggering conditions are defined for the system such that specified changes in time or specified changes in any system variable can cause triggering of a given log into one of two active states. Generally, a Free log state represents the log number and is a log number list without names or page assignments. a Defined but yet inactive log state includes names only. An active log includes both names and values correlated with times or time intervals, and an Active outputting log state includes not only names and values, but also a demand for the printing or displaying of a log. If a log is changed or triggered to the active state or to the Active outputting state, then the log data is stored in the proper log page field at the proper index location. The log page format is designed for use with page oriented printers, wherein each page includes a log number, and a log heading containing the names or identification of each member of the log.

These names are individually arranged in the heading at the top of the page in separate columns. In addition, each log page includes the time indication of the data on each line.

Generally, the program is designed to handle all details following the request by a human to place or change a point in a log, without any further human intervention. The program is designed to define log lists, report or remove members of the lists and to allocate pages. The program also is designed to be triggered by events or times, to set and control printout. Also. the program is designed to control log status. The use of the universal format with named system variables. the formatting and storage of data in log page field and the final format of the page oriented printout provides a system with the ability to easily change the types of logs, i.e., change the log members or add to the logs.

The present invention also provides a system and method of deriving the ordered sequence of interrupt events sensed by detection devices connected within a protective circuit wherein such detection devices are characterized by a time delay between the sensing of a predetermined condition and the actuation of their associated switching contacts, comprising means for detecting the change of state of the respective switching contacts associated with each of such detection devices, means for storing values of time delays associated with each of said detection devices, such time delays representing the known delay for a particular contact between its switching time and the actual time of occurrence of the event at the associated protective device, the time of actuation of such switching contacts being detected by the system, means for subtracting the stored time delay values from the detected times of actuation of the switching contacts of the respective devices to produce a corrected time of initiation of the event at the respective devices, whereby a corrected sequence of events is derived which indicates the correct order of occurrence of the events at the devices and, consequently, the initial cause of the event.

The storage and computations are carried out by the monitor and results computer system of the present invention which receives indications of the real time of switching of the device contacts and applies the associated corrective time delay for the particular contacts to produce the actual time of activation of the protective device. The system and method according to the present invention is thereby able to determine the actual interrupt event which initiated the protective devices.

The present invention also provides an alarming system and method which includes the assigning of an alarm limit value for a measured system variable at a given point in the system, scanning such point for the measured system variable even after such an alarm value is detected, calculating and applying a second alarm value representing a significant change (a delta) in the measured system variable from the last alarm value, and outputting the system variable information existing at each of such realarrn values.

The method also includes the setting of a fixed significant change (a delta) associated with the measured system variable of a point whereby the second alarm and any subsequent realarms would ordinarily be set off when the measured system variable departs from the last alarmed value by this fixed amount. In addition, the method includes changing this delta for a given point by selecting a multiplier which is applied to the fixed delta to produce a different delta which then represents the current value of the significant change in the measured system variable. This current delta will require the next alarming of the measured system variable value. The use of the multiplier to calculate a significant change of the system variable value by which the second or any subsequent alarm is to be set off allows the application of discretion in selecting only those very important alarm conditions to be outputted, thereby minimizing the number of alarm outputs.

A CRT device is provided for outputting the alarm information and instantly displays eachh alarm, when first detected, on the next free line above the most recent new alarm, starting at the lowest line of the alarm area of the CRT screen and moving upwards. When an operator acknowledges the alarm information, the alarm message is automatically changed to a reduced format wherein the current value, current direction, current deviation from the alarm limit value and current duration of the alarm is updated at the scan frequency or the calculation frequency of the measured point. When the CRT screen is filled with alarm information, that is, the top line of the CRT alarm area is occupied, the oldest group of alarm messages at the bottom of the screen is transferred into a system memory for alarm backlog information and the alarm information on the lines above those transferred shall be compacted downwards, thereby permitting entry of the new alarm at the first free line above the existing displayed alarms of the alarm area.

When the value of a measured system variable at a point was previously detected and displayed in the new alarm condition, and such point is further detected as having changed by a significant amount by crossing the computed delta value above or below the last alarmed value, and such point is not on the no alarm or normal side of the alarm limit, then such point will be displayed on its present line of the CRT screen in the new alarm fonnat until acknowledged by the operator, at which time the alarm information is returned to the reduced format. However, if the measured system variable alarm message had been previously moved into the backlog of alarms, the alarm message shall be removed from the backlog and placed on the next free line determined in the alarm area.

It is to be understood that, as used herein, the term named system variable includes a measured system variable, and vice versa.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a general block diagram of the monitor and results computer system of the present invention;

FIG. 2 shows a printer output format for a log page, illustrative of the present invention;

FIG. 3 is a block diagram showing the four log states;

FIG. 4 is a generalized system operation flow diagram;

FIG. 5 is a more detailed operations flow diagram of the diagram shown in FIG. 4;

FIG. 6 is a representation of the operator/engineer panel;

FIG. 7 shows a flow chart of the operation for defining a log;

FIG. 8 shows a flow diagram of the operation for changing the status of a log;

FIG. 9 shows a flow diagram of the operation for controlling the collection and/or outputting of log data;

FIG. 10 shows a protective circuit connected to the computer control portion of the system which computes the actual sequence of events detected by overload and protective devices;

FIG. 11 shows a graphical representation of a curve plot of a measured system variable at a point, with the set alarm values, the set realarm values and alarmed values drawn to illustrate the alarming system;

FIG. 12 shows a CRT screen having an alarming area for displaying alarm information in accordance with the format of the present invention;

FIG. 13 shows a generalized functional block diagram of the alarming system;

FIGS. 14A, B, C, D, and E show the sequence of presentations of the log trend;

FIGS. 14F, G, H, I and J show the sequence of presentations in a prior art trend display;

FIG. 14A is a graphical representation of a tuned output signal (Believed Value) as the input signals are varied;

FIG. 15B is a block diagram of a tuning system for deriving an output (Believed) value used for system maintenance; and

FIG. 16 shows the method for deriving a Believed Value and accordingly applying system maintenance.

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a block diagram of a monitoring and results computer system used for aiding the operation of processes such as occurring in power generation plants. The system is generally shown by a block diagram. Block 10 refers to the sensing devices throughout the plant that provide the information to the computer system in analog, digital and/or pulse form. Block 11 represents the interface and filter circuits for filtering and conditioning the digital and pulse type signals and interfacing them with the computer system either through the CPU and/or the input/output processor. The block 12 represents the filter equipment and the scanning devices to handle the analog signals. Block 13 includes the control of the multiplexing for scanning. Block 14 is the representative of the logic and arithmetic circuits associated with the CPU. Block 15 is the programming and programming system that directs the logic arithmetic circuits 14 and memory accesses to perform the desired sequence of instructions yielding the monitoring services. Block 16 represents the actual CPU internal control. The computers used in this function are mainly interrupt type machines and represent a small to medium level CPU with respect to the present art. Multiple CPU s are also utilized where required. The systems shown usually include multiple levels of memory and high memory transfer rates. Block 17 shows the high speed working memory. Block 18 represents a secondary level memory and block 19 represents tertiary level memories. Various levels of memory are utilized depending upon the speed of response required for the programming contained therein. Block 20 represents the input/output processor having the logic, control and associated memory mechanism for processing, formatting, etc., all system input and output data, and for regulating the connections among system information units and transfer control of information needed to be exchanged or transmitted between external peripheral devices and the internal memories. Block 21 represents the hard copy output devices such as printers and/or printer plotters of various types. Some of these devices 21 are used for permanent historical records, others for the printing information of temporary or tear off" use in operations. Block 22 is a group or groups of alphanumeric presentation devices, such as CRTs for display of information of immediate or transient rise that doesnt require hard copy. Block 23 is a group or groups of combination alphanumeric and graphic display types of CRTs or graphic types, for use similar to devices 22 but with pictorial capability. Block 24 represents a combination type CRT that is used both for display and in conjunction with the operator/engineer keyboard console requirements which are shown by numeral 25. The block 26 represents interfacing circuits providing translation and adaption equipment required to pass information from the subject system to the other data systems.

Generally, the system shown in FIG. 1 permits the functioning as will be described in detail hereinbelow. The logging system included in the system of the present invention is designed for use with page oriented printers. An example of the printer output format for a page is shown in FIG. 2. In page oriented printing, each of the system logs is identified by a unique number indicated at numeral 30 as Log 66, and a log constitutes a group of data associated with such log. Each numbered log has associated therewith an English identification indicated at 31, which is assigned from changeable programmer input equipment and from an on-line change or compiling system. This English identification, i.e. Turbine Inlet Conditions, is prined on each page in the log. Each log is made up of a series of pages, such as up to 10 pages, with each page containing a multiplicity of system variables, such as 16. In FIG. 1, the comers of the page define the log number 66 and page number 1 as 66/1. Each system variable in the page has a capacity of, for example, '40 lines of time-sequenced or other readings. I

Included in the log heading are the year, month, day of the month, day of the week, hour, minute, seconds, and time interval between logs for the data on the log page. Also, as indicated by the bracketed area by numeral 32 is a list of the point numbers together with an english description of each of these points. In the exam- I ple shown, there are 16 points respectively set forth in the 16 columns listed across the page. As shown by the heading area 32, column 1 is a listing of times, column 2 is a listing of the main steam at throttle, etc.

In addition to the log heading, each page includes heading and data identification information for each variable assigned to that page in accordance with the sample shown in FIG. 2. Thus, the page 1 of each log may include as one system variable the time of the data on that line. The logs can be assigned at repeat collection frequencies extending, for example, from one second to one day.

The system specifies an organized naming system for system variables that is constant throughout thereby simplifying the task of selecting and requesting information from the system. The system provides a method of grouping associated operating information, which is organized on the basis of functional lists, referred to herein as Log pages, so that simple requests will generate all associated information. As will become apparent from a reading of this specification, the Log page lists can be easily created by non-computer trained personnel and modified by the plant operators and engineers. The logging system is organized so that hard copy is generated on a page at a time log output, thereby making effective use of non-impact low maintenance printers. Also, the page oriented logging system permits continual acquisition of desired log data with the op.- tion to receive the latest page or pages of data upon demand or upon the occurrence of a predefined event.

This system also facilitates the generation of a graphic display of the trends of selectable data from active log pages. A Log Trend CRT can be used to trend information on the screen of one or more points in any active log or logs. A trend information display can be initiated by the demand panel to display trend information such as, identifying heading, Pen ID, Point ID, English identification, quality, present value, present engineering units, scales, and others. The request for Trend Pen Recording and for CRT log trend display can be generated and controlled from the operators panels. All points assigned to the operators recorders can be identified and the current value displayed in a specified format on the Trend Information CRT. It is noted that the CRT display of log output data can be used for outputting as an addition to or substitute for a log page printer.

The page oriented printed format according to the present invention comprises a given log content in a full page of information with several points of information located on one line for a given time. Thus, a request by a user for a given log will provide a page of printed information with the present log time and the previous 30 or 40 log lines of information for the same log. This is ccontrasted with some prior art logging formats which print out substantially a different log on each successive line intermingling unrelated sets of information with one another. I

The logging format makes it more practical to have a larger quantity of information in storage in memory such as the names, the addresses or location in memory and the contents or value of the names in memory. Of course, the amount of information contained in memory will depend to a great extent on the trade-off between the amount of memory available as against the processing time limitations. Generally, with the page oriented printing technique according to the present invention, the memory comprises a pool of pages of information with each page of information similar in content to the data to be printed out on the printer for a given log. Of course, the data in memory can be assembled to a lesser degree than that described above in which case processing and assembling of the data into final form for a page will be required.

In the page oriented printing format a printer may typically accommodate 16 columns of information. Since many of the logs contain morethan 16 items of information at a given time, then the pages of print are arranged in a fashion to accommodate a large number of columns of information for a given log, such as 160 columns of information. In this example, 10 pages of print will be arranged in a strip in series, with each page comprising 16 columns of print for the same log all on a time synchronized basis. Thus, page 1 may contain data values for a first 16 names or points of information at various times indicated, page 2 will contain data points 17 through 32 taken at the same time as the data on page 1, page 3 will contain information for points 33 through 48, etc. Further, the heading on a given page need not be changed for each line on such page since each of the page lines contains data associated with the points or names in the heading at the columns on the top of the page.

As an example, assuming that a single log contains 273 characters or 33 names with data for each point at a given time and that single page contains 16 columns, then 3 log pages will berequired to present this data. While this ordinarily would require a very wide paper, the page oriented printer arranged the pages in a strip series arrangement.

The system includes a naming scheme such that related items have one unique basic or root name throughout the system. The root name and suffixes are also referred to as point identication or ID number. All references to a point by the operator and the source language programs use the basic name plus any desired 10 suffixes. As an example, a basic name can have the form: PNNNN, Where:

P A prefix from the list below NNNNN A number from 0 to 9999 The prefix can be assigned according to the following:

A (Or Blank) Analog Input B Boolean/bit C Constant D Digital Input F Fast Calculation G Spare (Reserved for GROUP NUMBERS) H Spare I Summation Boolean Changes L Spare M Memory Location P Performance Calculation R Relay Output S Special Analog (Composed point) T Maximum of N Points W Minimum of N Points X Variable from Common The suffixesfapplied to the basic name for indicating processing or transformation on a point is instituted by appending the transform-related identifier to the basic root name. Suffixes can be multiple-level. At that time, the new point is created. The suffix can be consistently assigned according to alpha representations, such as A=Periodic Average, B=Periodic Minimum, C=Continuous RunningAverage, D=Daily Average, F=Daily Minimum, etc

All analog and digital type variables are stored in the computer memory with a quality code associated with the value which is, for example, in range of 0 through 3. The quality code is generated along with the value and is always propagated through transforms and calculations. Data quality levels can vary between the numbers 0 and 3 where the 0 represents good data quality and the 3 represents bad data quality. All printed or displayed messages are adapted for including a quality identifier along with the value.

In order to make the system operable the following needs of the operator must be met: (1) requests that the log information be presented immediately; (2) requests that the log content may be changed; or (3) requests that the log information be presented at specified time intervals, i.e., every hour. Each log may be in one of the following four states.

Every log carries with it a built in trigger, i.e., IF statement which is selected by the operator by, for example, activating log 44 if D103 (pump contacts) go off and if an analog value goes above a certain defined state or value, or system activity previously determined or changes of quality.

Refem'ngto FIG. 3, the four log states are shown in a block diagram form. Here, the Free (Undefined) Log State 0 represents the log number without labels in the log and without page assignment. Generally, the Free Log State 0 is a log number list without names. The Defined (Inactive) Log State 1 includes names. The Active (gathering but Non-printing) Log State 2 includes both names and values at specified time intervals of collection. The outputting (gathering and Active Printing) Log State 3 includes not only names and values but is outputting as well as collecting.

In the Free State, the log is available for definition and uses no pages. A request to print or report a Free 1 1 Log shall report to the requesting station immediately the message that the log is Free.

In the Defined State, the log has some system variables assigned to its columns but it is not gathering or printing. Logs are moved from the Free State to the Defined State by panel function and/or the on-line background compiler. As the log is Defined, the Operator designates the column and the ID of the system variable assigned to that column. Column number in excess of 16 causes the system to automatically utilize additional page(s), and the mechanism continues for multiples of 16 up to pages. Logs with high collection/printing frequency require 2 memory pages per log page to provide time to print. The Operator can insert blank columns for formatting as he desires. A request to print or report a Defined Log shall cause the standard log headings, variable heading, and one line of the latest available value of the corresponding system variables. All of this is printed on a Page basis by the printer associated with the requesting panel, unless a different printer is requested or is automatically substitutedby the system itself.

A Defined Log may be moved to the Active State by either panel function or change of state to a prescribed direction of a flag bit set by an event triggered program. In moving from Defined to Active State, a collection frequency is specified either by the panel function or the initiating program or the previously designed frequency if a new one is not supplied. In the event of a conflict, the program prevails. The Active State causes the logging system to collect the values associated with the system variables contained in its page list(s) at the respective frequency defined for the owning log. As this data is collected it is written to the system drum/- disc (secondary) memory. Each log page contains, for example, enough storage to provide heading information and forty lines of data. Output has a total of 52 lines of 132 characters/line. Three additional lines of storage are provided to buffer for the print time. The logging program continues to overwrite the oldest line, thus keeping a full Page of log available for instant printing on demand. When the"fast logs (i.e.: interval less than 30 seconds) are moved to the printing state, two Pages can be alternatedone being printed while the other is being filed by the logging program.

The state change from Active to Outputting is initiated by panel function or by prescribed direction change of state of a second Flag bit. When output is requested by panel function, the present contents of the log is immediately printed, and each new Page of data (forty lines) is automatically printed until the panel function requesting outputting is cancelled. Where printing is initiated by event, the digital action program controlling the print determines both the number of readings to be taken before printing is initiated and the duration of the printing. In any case, where printing is initiated by event or event delayed, the time of the initiating event will be stored as a line of data in Column 1, and asterisks written into that corresponding line for all other columns of that line. All logs with event triggering are capable of manual triggering with or without delay to print.

Either the Active or the Output Report of an Active log will cause full headings and data of the current page to be printed on the printer associated with the requesting panel, unless otherwise requested.

As an example, Pages to be assigned for logging can be taken from a system pool of 280 pages. Assuming 12 that the logs described previously are numbered 1-99, this pool includes the Pages for Series logs as well as Special Logs.

Series 100 logs include;

A: Tabularized log 101 which is the formal log of up to 10 Pages;

B: Log 102 which includes the formal Daily Logs of up to 10 Pages;

C: Log 103 which is the Operational and TurbineTrip Analysis of two Pages, and one-second frequency;

D: Log 104 which is the operational Data and Turbine-Trip Analysis Log up to five Pages of Fifteensecond frequency;

E: Log 105, 106, 107 which are assigned to the Turbine Data Log for operation at predetermined value openings once a day, and turbine roll to half load, or trip to turning gear plus 10 minutes, and also from certain analog or contact variables associated with the turbine exceeding preset limits; and

F: Log 108 to 110 are spare.

Every log has the abiltiy to take on the above defined four states and to move forward and backwards within such four states as shown in the arrows interconnecting the blocks. With the above logging system, no programmer is needed on call since the program in operation is under the full control of the plant operator or user.

There are generally three types of system variables, these being of the analog type, the boolean type and the reference type. The analog type varibles consist of points having values represented by more than one bit plus quality. Analog type variables include analog inputs, constants which are generated by the program or entered via the operators panel, fast calculations, performance calculations, common variables and others. Boolean type variables consist of points having values represented by one bit plus quality and include variables such as digital inputs, relay outputs and boolean bits (flags). Reference variables provide memory location identification and include memory locations in core or drum/disc for the purpose of references to the contents of those locations.

The logging system can be used to provide both tabular data and graphic or curve representations of the system variables. The curve representations are generally used where the logging system is in the active state and the data is moving rapidly or has just gone into alarm status. Here, the system is programmed to produce curve vectors to define the various operations. The system finds the desired information via the log lists and produces a log trend of the point at the present time and during the period of 40 logged readings preceeding the present time, such as for the last 40 seconds or 20 minutes, etc. The generation of a log trend for a point is, therefore, made by a system which can be characterized as an on line real time system.

The system includes a log trend CRT display which can show trends of up to four points, for example, in any active log or loop. When trend is initiated by operation of ANALOG TREND (Button l26b shown in FIG. 6) the system displays the equivalent, suitably scaled analog tract from the values stored in the appropriate log page (FIGS. 14A 14E). FIGS. 14F-J represent a prior art display (identified as WITHOUT) in which there is no trend presentation at the time of commanding a trend presentation since such a display included no structured stored data.

A time scale grid can be displayed according to log frequency. The trace can be suitably updated and ad- 

1. A method of producing a value which is most representative of a condition determined by a plurality of physical measurement input devices which are responsive to the Condition which can change, the method comprising the steps of: a. receiving signals from a plurality of input devices, the signals representing the values which are responsive to the condition; b. averaging the value represented by each of the received signals with the value represented by each of the other received signals to derive a set of averages; c. selecting a predetermined non-linear factor which corresponds to the probable disagreement between the received signals; d. forming a normalized average for each of the set averages by dividing each average by the non-linear factor; e. subtracting from the value represented by each of the received signals the value represented by each of the other signals to derive a set of absolute differences: f. dividing each of the absolute differences by the non-linear factor to provide a first set of normalized differentials; g. selecting a predetermined non-linear power which controls the degree of weighting for each signal as a function of its deviation from the other received signals; h. raising each of the first normalized differentials by the selected non-linear power; i. deriving a weighting factor for each average whose value is a function of its normalized average and its normalized differential raised by the selected non-linear power; j. weighting each average by the weighting factor derived for that average; and k. forming a composite of the weighted averages to thereby derive a value which is most representative of the condition.
 2. A method in accordance with claim 1 in which the step of receiving signals from a plurality of input devices which are responsive to the condition comprises receiving signals representing at least three values which are responsive to the condition.
 3. A method in accordance with claim 1 in which the step of receiving signals from a plurality of input devices which are responsive to the condition receiving at least two signals representing values responsive to the condition and receiving a signal representing a reference value which corresponds to the value related to the normal state of the condition.
 4. A method in accordance with claim 1 in which the step of receiving signals from a plurality of input devices which are responsive to the condition comprises receiving a reference signal corresponding to a value which is substantially displaced in one sense with respect to the expected value of the condition and receiving another value displaced in the opposite sense from the expected value for providing a plurality of values where a plurality of values responsive to the condition are not available.
 5. A method in accordance with claim 4 in which the step of receiving a reference signal corresponding to a value which is substantially displaced in one sense with respect to the expected value of the condition comprises receiving a reference signal approaching a zero level and in which the step of receiving another value displaced in the opposite sense from the expected value comprises receiving an additional signal approaching an infinite level.
 6. A method in accordance with claim 1 and further comprising the step of selecting values to be received at least a portion of which have substantially corresponding transient response and forming the composite of weighted averages during the presence of transients in the values being received, the substantial correspondence in transient response of the values being received reducing the discrepancy of such values from the value representing the true condition.
 7. A method according to claim 1 in which the step of weighting includes the step of multiplying each average by the weighting factor derived for that average.
 8. A method according to claim 1 in which the step of forming a composite includes the steps of: i. summing the weighting factors to form a composite weighting factor; ii. summing the averages after each average has been multiplied by the weighting fActor derived for that average; and iii. dividing the sum of averages of step (ii); by the sum of weighting factor of step (i).
 9. A method in accordance with claim 1 in which the step of deriving a weighting factor for each average comprises the steps of: dividing each of the raised normalized differentials by its corresponding normalized average to form a set of ratios; summing each of the ratios with a predetermined constant; and inverting each of the summed ratios to thereby form the weighting factors.
 10. A method in accordance with claim 9 in which said predetermined constant has a value equal to
 1. 11. A method in accordance with claim 1 further comprising the step of tuning the forming of the composite of the weighted averages, step of tuning including: repeatedly varying the output of one of said input devices over a likely range of values including a value representing a signal received from an input device which is in a failure mode while holding the outputs of the other input devices at appropriate levels; for each repeated variation selected different non-linear factors and non-linear powers; for each repeated variation comparing the characteristic of the composite of said weighted average with the desired characteristic of the value of the condition; whereby the non-linear factor and the non-linear power result in a characteristic most representative of the desired characteristic can be derived.
 12. A method in accordance with claim 1 and further comprising the steps of: a. deriving the difference between the value representing each of the received signals and the composite of said weighted averages to form a second set of absolute differences; b. averaging the two smallest absolute differences of said second set to form an average difference; c. marking the received signals associated with the smallest differentials of the second set thereof as good; d. determining the larger value of the average differential and the non-linear factor, the larger value being a test factor: e. comparing the test factor with a predetermined multiple of the non-linear factor to determine whether the test factor is in excess of the predetermined multiple of the non-linear factor; and f. additionally marking all received signals suspect for maintenance checking when the test factor is in excess of the predetermined multiple of the non-linear factor.
 13. A method in accordance with claim 12 and further comprising the steps of: a. selecting the largest absolute difference of the second set of absolute differences; and b. comparing the selected largest absolute difference with a unique value which is a predetermined multiple of the test factor to determine whether the received signal related to the selected largest absolute difference of the second set is bad or has excessive discrepancy.
 14. A method in accordance with claim 13 and further comprising the step of: further marking a received signal with one of predetermined designations of good, bad and having excessive discrepancy from the value which is most representative of the condition, the step of marking being in response to the step of comparing the selected largest absolute difference with the unique value.
 15. A method in accordance with claim 13 in which the unique value is a predetermined first multiplier of the test factor, the product of the first predetermined multiplier and the test factor defining an excessive discrepancy of a received signal from the value which is most representative of the condition.
 16. A method in accordance with claim 15 and in which the step of further marking comprises marking the received signal related to the selected largest absolute difference of the second set as being bad.
 17. A method in accordance with claim 16 and in which the step of further marking comprises marking the received signal related to the selected largest absolute difference of the second set as being suspect.
 18. A method in accordance with claim 17 in which the unique value is a predetermined second multiplier of the test factor, the product of the second predetermined multiplier and the test factor defining an undesirable discrepancy which is less than an excesive discrepancy of a received signal from the value which is most representative of the condition.
 19. Apparatus for producing a value which is most representative of a condition determined by a plurality of physical measurement input devices which are responsive to the condition which can change, the apparatus comprising: a. means for receiving signals from a plurality of input devices, the signals representing the values which are responsive to the condition; b. means for averaging the value represented by each of the received signals with the value represented by each of the other received signals to derive a set of averages; c. means for selecting a predetermined non-linear factor which corresponds to the probable disagreement between the received signals; d. means for forming a normalized average for each of the set averages by dividing each average by the non-linear factor; e. means for substracting from the value represented by each of the received signals, the value represented by each of the other signals, to derive a set of absolute differences; f. means for dividing each of the absolute differences by the non-linear factor to provide a first set of normalized differentials; g. means for selecting a predetermined non-linear power which controls the degree of weighting for each signal as a function of its deviation from the other received signals; h. means for raising each of the first normalized differentials by the selected non-linear power; i. means for deriving a weighting factor for each average whose value is a function of its normalized average and its normalized differential raised by the selected non-linear power; j. means for weighting each average by the weighting factor derived for that average; and k. means for forming a composite of the weighted averages to thereby derive a value which is most representative of the condition.
 20. An apparatus in accordance with claim 19 and further comprising: a. means for deriving the difference between the value representing each of the received signals and the composite of the weighted averages to form a second set of absolute differences; b. means for averaging the two smallest absolute differences of the second set of absolute differences to form an average difference; c. means for marking the received signals associated with the smallest differentials of the second set thereof as good; d. means for determining the larger value of the average differential and the non-linear factor, the larger value being a test factor; e. means for comparing the test factor with a predetermined multiple of the non-linear factor to determine whether the test factor is in excess of the predetermined multiple of the non-linear factor; and f. means for additionally marking all received signals suspect for maintenance checking when the test factor is in excess of the predetermined multiple of the non-linear factor.
 21. An apparatus in accordance with claim 20 and further comprising: a. means for selecting the largest absolute difference of the second set of absolute differences; and b. means for comparing the selected largest absolute difference with a unique value which is a predetermined multiple of the test factor to determine whether the received signal related to the selected largest absolute difference of the second set is bad or has excessive discrepancy. 